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ACD/Labs Blog

Arvin Moser
Where a COSY or TOCSY spectrum can be a challenge for a structure with severe spectral overlap, collecting an HSQC-TOCSY spectrum can be a better choice. An HSQC-TOCSY experiment stands for Heteronuclear Single Quantum Coherence-Total Correlation Spectroscopy and other variants include HMQC-TOCSY, HSQC-COSY, etc. Depending on the mixing time, the hybrid experiment generally offers information...

Ryan Sasaki
Above is a picture of an example output of our automated structure verification routine. This highlights one of the strengths of our automated verification approach, one Phil Keyes calls a “fringe benefit” (See slides 39-42) in that following verification, you get an estimated assignment starting point. The output is a report, or spectrum file that...

Arvin Moser
Part 1 of the series Teaching and Learning by Spectral Data explored the difference between presenting an NMR problem set to a student in the form of an alphanumerical text or as an actual NMR spectrum. Continuing on the same problem set, another issue arises. Is the information on the elements and the 1H NMR...

Ryan Sasaki
In yesterday’s post I pointed you to an article that has become the most accessed article of all time in the Journal of Cheminformatics, co-authored by representatives of ACD/Labs. This article is a very comprehensive outline of the different approaches, developments, and successes of the development of CASE (Computer-Assisted Structure Elucidation) systems . I hope...

Ryan Sasaki
An article co-authored by several ACD/Labs scientists, the Russian Academy of Scientists, and ChemZoo, Inc. has been generating a lot of interest over the past year. In fact, this article entitled, “Computer-assisted methods for molecular structure elucidation: realizing a spectroscopist’s dream“ is the most accessed article of all time, on the Journal of Cheminformatics website....

Arvin Moser
There are many ways to teach the process of elucidating unknown structures. Offering a student a visual guide, such as seeing firsthand a spectral dataset, can enhance the learning process and better equip the student on future work. Presented below is a typical elucidation question from a university test. The numerical values have been extracted...

Arvin Moser
In the constant pursuit of new pharmaceutical drugs, process chemists (sometimes referred to as medicinal or synthetic chemists) must investigate all impurities detected in a new drug manufacturing process. The chemist’s procedure is simple: identify, elucidate and synthesize each and every single impurity. The chromatogram (UV detector set at 254 nm) below shows three peaks....

Arvin Moser
After a long and arduous attempt at an elucidation, it is quite common to be left with more than one candidate structure. In some cases collecting more data is not an option and an exhaustive database/literature search turns up nothing useful, the alternative approach is to synthesize the proposed candidates and then compare the spectral...

Arvin Moser
Datasets for large unknown compounds tend to be complicated and typically require a lot of effort in distinguishing one signal from another. Having some background information about the unknown, such as a metabolite, a precursor, a derivative, etc. can be invaluable with the detail work needed to get through an elucidation. The 13C NMR spectrum...

Arvin Moser
With any type of data, there is an inherent risk of misinterpretation. My advice to elucidators is to consider multiple solutions and examine each one thoroughly. In the end, the answer to any problem set lies in tying together the bits of information in hopes of understanding the bigger picture. Recap of the problem: The...